How viable/practical would it be to attach a 1.7x magnification filter to the end of the FZ200's lens, boosting the 600mm maximum zoom to 1020mm- which would then put it up with the Canon SX50HS (1200mm) and new Fujifilm HS50EXR (1000mm)- while still retaining its constant 2.8 apeture?Would this create problems for Image quality, Zoom-ability of the lens, or any other issue?